Electric gauge



Dec. 19, 1944. H. T. RIGHTS ETA- 2,365,593

` ELECTRIC GAUGE Filed Nov. 19. 1942 fig-J.

ATTORNEY Patented i9,

" UNirEn STATE-s PATENT .l OFFICE l'. ascissa ELEcrnro GAUGE l y Herben r. nights. verona. and nenn L. nem-,

ardc,-Union. Drew Field, a., I, .Electric &

J., and Frederick J.' Altman, assignors to- Westinghouse Manufacturing Company, lEast Pittsliurgh, Pa., a corporation of Pennsylvania 'Appiieitionfivevember 19,1942, serial No. 4e6,142

"' s claims. (ci. 33147 This inventionjrelates to devices lfor measuring mechanical displacements and dimensions and it has particular relation to electrical devices having an electrical output dependent on a mechan;v ical displacement or dimension 4to be measured J Because of their sensitivity and flexibility, electrical measuring instruments have been employed a u I i dary windings, the division of magnetic iiux between the secondary windings being dependent ,0n the value of, the dimension to be measured.

Other objects of the invention will be apparent from the following description taken in conjunction with the accompanying drawing, in which:

for the purpose of measuring mechanical disl placements and dimensions. Since such devices must operate with extreme accuracy, it is desir- -able that they have a minimum oi parts subject Ato mechanical and electrical variations.-

` Figure 1 is a schematic view with parts shown gin elevation andparts broken away of a measuring device-embodying the invention,

Fig. 2 is a-graphical view showing the operating characteristics ci the measuring device of In accordance with the invention, an electrical measuring device for measuring mechanical disi placements and dimensions'is provided with;a

magnetic'circuit having only two relatively mov,

able parts. These'parts may include an E -shaped magnetic member having a pairof outer legs' and an inner leg: 'An armature member is disposed for-movement between Athe outer legs in accordance with a dimension or displacement to be measured. Such a masneticstructure provides two magnetic circuits. each -includingfone vof `the outer legs of the magnetic member. The u inner leg is common .tov both of the circuits.

For energizing the magnetic structure, -a winding which may be termed a primary winding, is disposed on the inner leg and is energized from a source voit voltage. A separate winding, which may be termed e. secondary winding. isdisposed ,oneach of the outer legs 4and has induced therein a voltage 4whichis dependent on the value ofthe Y magnetic ilux passing through the associated outer leg. Suitable translating means suchas an. electrlcalmeasuring instrument isprovided for measuring the difference in induced voltages -of Fig. 1,

Fis. 3 is a view in front elevation of a completev measuring'device embodying the invention,l

Fig. i is a view insidev elevation with parts in vcross section of a gauge\head suitable lfor the device o! Figs. 1 and 2,

Fig. 5 is azview in cross section taken along the line V.V of Fig. 4, and.

Fig. 6 is a view in cross section taken along the line VI-VI of Fig. 4.

Referring to the drawing, Figure 1 shows an electrical gauge device' which includes a gauge head -This gauge head is provided withan E-shaped magnetic core 2 having al centrally disposed-leg 3 and outer magnetic legs .l and 5. A.

magnetic armature 6 is positioned adjacent the centrally disposed leg l for movement between the outer legs 4 and 5 of the magnetic core 2.

the secondary windings. Such digerence is'con-` trolled by the displacement oi' the armature mem- .Y ber relative to the associated E-shaped magnetic v only-two relatively movable parts.

s n n s sau fui-tnerbi'eet ef'theinve'nuento jprovlde an electrical-measuring vdevice responsive By inspection of Fig. 1, it will be observed that Vmovement ofthe magnetic amature l serves to vary simultaneously in reverse directions air .gaps

between the magnetic amature 8 and 'each oi the legs 4' and' i. Consequently, movement of the armature serves to vary the reluctances of two magnetic paths. one of which includ'es Vthe outer legl, and the second of which includes the outer leg 6 of the magnetic core. Both ofthese magnetic paths include as a common' portion -vthe cen trally disposed leg 3F of the magnetic core. -'.ll'he core 2 and the armature 6 are formed. of magnetic :material preierablywhaving high electrical resistivity, such as silicon steel or a material similar to that disclosed invUn'ited States Patent No. 1,807,021 and marketed under the trade-'name Hipernih The magnetic material may be laminated oritmay' be employed in solid section ',form.

to mechanical ts and dimensions wherein a magnetic structure is provided two magnetic paths andhaving a magnetic portioncommentotlietwo,illclrneticpaths.`

' It is an' additional object oi' the invention to provide an electrical measuring device vfor. deter- Y mechanical .dimensions whereina magnetic structure is provided for directing magnetic nuxiromaprimaiywlndingthiwghtwo secou- 'The maimeticarmature 8 is mounted on a supporting member 1 which conveniently may beV formed 0f; a non-magnetic material, -such as brass. Movement oithe magnetic armature-is confined to a path de tern'iine i by two leaf springs c and i which also may be formed of brass or' anyjsuitable material. One end of each of the 'siu'ingslandlisrigidlyattachedtothesuppol't-y ,ingmemherlinanyniitabiemannen Theremalningendsofthesnrinuareattachedtothe Hexureoitheslirlngslandtpermitsmoveascensos 33 into direct current for energizing the instrument. Although any suitable rectiiler lmay be Since movements o! the magnetic amature 3- -I Amodify the reluctances of the magnetic paths including, respectively, the legs 4 and 5.- the resulting change in' the reluctances may be employed to indicate the degree oi movement 'ofthe magnetic armature. For this purpose the centrally `disposed leg'3 is surrounded by a winding 3|! which is energized from a source of alternating current 3I. Preferably the source of source. To permit variation of the voltage applied to the winding 33, a potentiometer 32 may be interposed between the source 3| and the winding 3l. By operation of a movable tap33, the voltage applied to the winding 3l may be varied, if desired.

- Alternating current flowing through the .winding 3l produces'an alternating magnetic ilux in the leg 3. When the magnetic armature 5 is mid-.way between the legs 4 and 5, the alternating magnetic ilux divides equally between the legs 4 and 5. Movementof the magnetic armature 6 from this mid-position increases the reluctance of one of the magnetic -paths and de- -passing through the associated leg onthe magnetic core 2. The windings 34 and 35 are connected in opposition in-a series circuit by meansof conductors 36, 31, and 38. Consequently, when the voltage induced in the windings 34 and 35 are equal, no current flows in the series circuit. If the windings 34 and 35have equal numbers of turns, equal voltages will be induced therein when the magnetic armature 5 is positioned mid-waybetween the legs 4 and 5 of the magnetic core 2. When the magnetic armature 6 is displaced from this mid-position, the voltages induced in the windings 34 and 35 'are' not equal, and the resulting diierence in voltages produces a currentvin the series circuit. This current may be measured by a suitable measuring instrument connected between the conductors 31 and 38.

In the specic embodiment illustrated in Fig. 1, the measuring instrument may take the form .of a conventional permanent-magnet, moving- Y coil instrument 39 which is sometimes referred to as a DArsonval instrument, and which has excellent sensitivity. Since the instrument 39 is a direct-current instrument, a suitable rectiiier 40 is connected between the instrument 39 and the conductors 31 and 38 to convert the alteremployed, the rectiiier 43 conveniently may be a barrier-layer rectifier such as a copper-oxide rec.. tiiler. Such copper-oxide rectiflers may be connected in the familiar bridge form illustrated in Fig. 1 for providing full-wave rectiilcation of the alternating current. If desired the rectifier may have a iilter associated therewith for smoothing the rectified current supplied to the measuring instrument. Ordinarily such aillter is not required.

The operation of the gauge device illustrated in Fig. 1 may be understood more fully by reference to the graphic representation of Fig. 2. In

. Fig. 2 the voltage applied lto the measuring inalternating current 3| is a constant voltage natingA current flowing in the conductors 31 and 75 strument 33 is plotted as ordinates against the displacement of the magnetic armature 5 as abscissae. 'In Fig. y2,.the reference vaxes Y and X intersect at a point 0 which corresponds to that position of the magnetic armature 6 mid-way" between the legs 4 and 5. The characteristic of the gauge device illustrated in Fig. l is represented in Fig. 2 by the full line curve I-II.

By inspection of the curve I-lI, it will be observed that i'or a Vdisplacement of the magnetic armature 6 in one direction from its lmid-point, which will be assumed to -be an upward direction, as viewed in Fig. 1, for a distance d, the voltage applied to the measuring instrument has a value corresponding ,tothe point A in Fig. 2. However, it will be noted that the curve I--lI is substantially symmetrical about the Y axis. For this reason, a displacement of the magnetic armature 6 in a downward direction (as viewed in Fig. 1) for a distance -d results in the application of ah voltage corresponding to the point A' tothe measuring instrument 39 which is equal to the voltage corresponding to the point A.

Consequently, inspection. of the measuring instrument 39 would not indicate which of the distances, d or -d, is responsible for the measuring instrument indication.

- To avoid such ambiguities, movement of the magnetic armature 5 may be restricted to one Yside only of its mid-point position. For the purpose of discussion, it will be assumed that movement of the armature 6 from its mid-point position is permitted only in an upward direction. For such an adjustment, only that portion., of the curve I--II which lies on the right of the axis Y is employed.

By inspection of Fig, 2, it will be observed 'further that the curve I-II departs from linearity adjacent the axis Y. lThis departure from linearity is caused principally by the variation of the resistance of the rectier with respect to current. For these reasons, the magnetic armature 6 is permitted to move only in the range assuring a linear voltage output.

In operation a reference block having a standard dimension is positioned upon the platen I3. The gauge head I then is moved relative to the table I3 until with the pin I2 in engagement with the reference block, the indicating pointer of the measuring instrument 39 is at a predetermined point on the scale, such as the zero point.

'It will be assumed that the voltage necessary to work positioned beneathi the that represented by the point A indicates that pin I2 is smaller than standard.

It sometimes is desirable to change the sensitivity of the gauge device from that represented by the curve I-II in Fig. 2 to that represented by a new curve, such as the curve III-IV of Justed.

Fig. 2. Such a change in sensitivity may be eiiected, for example, by decreasing the voltage appliedto the winding 80. This decrease is obtained by properv adjustment oi the movable tap -88 with respect to the potentiometer 82. When- 4such a change in sensitivity is eiected, it becomes necessary to readjust the gauge head. The necessity for the adjustment may be understoodl from a brief discussion of Fig. 2.

When the sensitivity corresponds to the curve III-IV a deflection of the magnetic' armature having a value d produces a voltage equal to that represented by the point B on the curve HIJ-IV. This voltage is not suiiicient to actuate the pointer yof the measuring instrument 88 to the zero point on its scale. Consequently, the gauge head must be adjusted to provide a de iiection d' which produces .a voltage corresponding to the point C on the curve III-IV. Since this voltage is equal to that represented by the point A, the pointer Vof the measuring instrument 88 indicates the correct value. At the same time. the gauge must be adjusted to provide a vsuit- ,.able range of movement of the' magnetic armature on either side of the new center position represented bythe point B. These adjustments are discussed in the copending H. T. Rights et al. application, Serial No. 421,850,` iiled December 5, 1941 and assigned to the same assignee.

As shown in Figs. 1 and 3, the gauge head I maybe associated with any suitable standard which serves as a guide for a slidabl Il. This carriage has an opening for snugly receiving the pillar 54. A clamping screw 58 is provided for clamping the carriage at anyposition on the pillar 54 -to'which the carriage is ad- For adjusting the carriage 58, an -adjusting screw 8l isrotatably mounted in the -base 52 and a bracket 82 carried by the pillar 54. The bracket 82 and the base 52 permit rotation oi the screw 88 butprevent axial movement thereedly engaging the screw 88.

By lreim-.ion of the handle u, the carriage u 'may be raised or lowered with respectto the ltable II'to any desired position.' When the carriage arrives at the desired position, the clamping screw III may be manipulated .to clamp the o! this general type are well know'in the art.

, The gauge head1- may be secured in any desirable manner tothe carriage 58. rConsequently, movement of the carriage may be utilizedfor adjusting the gauge' pinII with respect to the the instrument 88 secured thereto by means of a suitable bracket 88. A

A suitable design for the gauge' head I is shown in greater detail in Figs. 4, 5 and 6'. As previously pointed out, the E- shaped magnetic core 2 and the magnetic armature 8 may be constructed ofany suitable soit magnetic material. In the speciiic embodiment of Figs. 4, 5 and 6, these parts areassumed to be formed or laminations. Such laminations tend tol reduce the iiow oi eddy` currents in the coreV and armature during v operation of the gauge.

The magnetic armature 8 is attached to its` supporting member 'I in any suitable manner as by means of a machine screw 88, which passes through an opening in the armature and is received in a threaded opening provided in the lsupporting member 1. In addition, the supportmoved simply by releasing the machine screw 8 and 8 with -ufshaped clamping members 18 for clamping the springs to the supporting member. A screw 80 may be provided for securing the upper clamping member 18 tothe supporting member 1. To facilitate` attachment of the gauge pin I2 to the gauge head, a machine screw 82 may bef-provided. for the lower clamping member 18 carriage Il .Crmly tothe pillar I4. Standards' 'table I8. In addition, the carriage Il may have 75 member.

having an-elongated head to.which the gaugeV pin I2 may be secured in any desired mannerb 'as by providing the gauge pin and associated screw with mating male and female threads. rIfhe magnetic core 2 may be secured to a supporting member 84 which is similar in construction to the supporting member 1. However, the

supporting member 84 need not be provided with pockets similar to the pockets 14 yfor providing a space between the legs 4 and 5 and the supporting 'I'he magnetic core 2 may be secured to the supporting member 84 by-means oi suitable machinevscrews 88. These screws also are employed for securing toi the magnetic core an insulating angle 86 which serves as a terminal` panel for the leads oi,thewindings"30, 34 and 85. The supporting member 84 alsotis provided with the clamping members 18 and machine screws l8II for securing the remaining ends vof the springs 8 and 8 thereto.

The vsupporting member 8 4, is, in turn, se-4 cured to a` plate 88 by means of machine screws 80. The plate '.88 may have a flange 82 about its periphery'fr cooperation with a cover 84 for the gauge head. This cover has an. opening 88 vpermitting passage of the gauge pin I2. therethrough. To exclude dust from the -interior oi the cover, a. ilexibls membrane198, such as one formed of rubber, may beemployed for closing the opening 88 without interference with the free motion or the gauge ,pin' I2. "The,cover 84 is securedto the plate `88by means of suitable machine screws III.-

-. For securing the gauge head `I to the carriage.

56, machine screws |82 may pass through openings in flange |84 formed on the carriage 58 into e threaded openings provided in the plate 88.

Conductors |06 may extend from the terminal panel 81 through an opening |08 in the plate 88 and through a conduit I| for connecting the windings to the instrument 38 and the generator 3|. The conduit may be attached to the gauge head by means of a clamp |I2 which is attached to the 'plate 88 by means of screws Il. It will be understood that the conductors |06 are connected to the leads from the windings 30, 3l and 35 at the terminal panel 81.

From the foregoing discussion, it is believed that the operation of the gauge as a whole is apparent. With the parts in the positions illustrated in Fig. 3, a reference block o f correct dimension is positioned on the table |3 beneath the gauge pin l2. The screw 80 then is rotated to force the gauge pin I2 against the reference block until the instrument 3 8 gives a desired ieading which conveniently may be a mid-scale reading. The clamping screw 58 then is operated to clampthecarriage rmly in its adjusted position. It will be understood that the instrument 39 may be a conventional measuring instrumentI wherein-the pointer occupies a lefthand position when deenergized, as illustrated -in Fig. 3. When the gauge pin y| 2 is adjusted for a reference block l2, a voltage is applied to the instrument 38` which corresponds to the value represented by the point A in Fig. 2. 'I'his voltage may be suillcient to drive the pointer of the instrument to its mid-scale position, thereafter positions of the pointer below mid-scale indicate that the overwork being measured is undersized. Conversely, positions above its midscale position indicate that the overwerk being measured is oversized. In Fig. 1, the work W on the table I3 is assumed to have the correct dimension. For this reason, the pointer of the instrument 39 occupies its mid-scale position.

When work is placed'on the table I3, the work engages the pin I2 and actuates the pin in an upward direction. Although. gravity alone may suffice tobias the armature 6 and its supporting member 'I downwardly 'into engagement with the work,`if desirable an additional bias may be ex` erted by the springs 8 and 8 for this purpose.

Movement of the armature in accordance with :s may'be calibrated directly in units of the dimension being measured.

lAlthough the invention has been described Vwith reference to certain specific embodiments thereof lnumerous modiiications 'are 'y possible. Therefore, the invention is to be restricted only by the accompanying claims as interpreted in view of the prior art.

We claim as our invention:

l. In an electrical measuring device responsive to mechanical displacements, an E-shaped magnetic member including a pair of 'spaced outer legs and an inner leg, an armature mem- .ber .of magnetic material extending between Y said outer legs. said inner leg being shorter than said outer legs to provide a face adjacent said armature member, said armature member being spaced from said outer legs to provide air gaps therebetween, means mounting said armature member for movement substantially parallel t0 said face of said inner leg to vary oppositely the air gaps between said armature member and said outer legs, said last-named means comprising a pair of leaf springs` connecting said armature member to said magnetic member, a winding on said inner leg for producing, when energized. magnetic fiuxes in said outer legs, and a separate wind-ing on each of said outer legs, each of said windings having a. voltage induced therein which is dependent on the magnetic flux passing through the associated leg of said magnetic member, said armature member having a contact element associated therewith, whereby displacements of said contact element relativeto said magnetic member simultaneously vary oppositely the magnetic reluctances offered to magnetic fluxes passing respectively through said -outer legs.

2. In an electrical measuring device responsive to mechanical displacements, a magnetic member, a magnetic armature element, means mounting said armature element for rectilinear motion with respect to said magnetic member in a predetermined direction, said armature ele- 'ment-having rst and second spaced surfaces disposed angularly with respect to vsaid predetermined direction, and said armature element having a third surface extending substantially parallel to said predetermined direction, said said first, second and third surfaces to denne with said armature element a pair of magnetic paths having reluctances which vary oppositely in response to said rectilinear motion of said armature element, a' separate electrical winding linkecl'with eachV of .said magnetic paths, and a winding effective, when energized, for producing magnetic iiux in both of said paths, said lastnamed winding linking both of said magnetic paths.

` 3. In an electrical measuring device responsive to mechanical displacements, a magnetic member, a magnetic armature element, means mounting said armature element for rectilinear motion with respect .to said lmagnetic member in a predetermined direction, said amature element having iirst and second spaced surfaces disposedangularly with `respect to said predetermined direction, and said armature element having a third surface extending substantially parallel to said predetermined direction, said magnetic member comprising a magnetic base portion and ii'rst, second and third magnetic legs projecting from said base portion, said magnetic legs having surfaces respectively extending adjacent and substantially parallel to said rst, second and thirdsurfaces to define with said armature element a pair of magnetic paths having reluctances which vary oppositely in response to said rectilinear motion of said armature element, a separate electrical winding linked with each of said magnetic paths, and a third electrical winding surrounding said third magnetic leg for producing, when energized, magnetic flux in both of said magnetic paths.

HERBERT T. RIGHTS. HENRY L. BERNARDE. FREDERICK J. ALmaN. 

